Coating apparatus



Mam]! 4 R. c. BENNER ET AL 4,253

- COATING APPARATUS I I Filed 001:. 27, 1932 2 Sheets-Sheet 1 INVENTORSRAYMOND c. BENNER Rome L.MELTON y HENRY P. KlRGHNER A TTORNEY March 19,1940." R. BENNER H M 2,194,253

COATING APPARATUS Filed Oct. 27, 1932 -2 Sheets-Sheet 2 INVENTORSRAYMOND 0. Banana Rome L. MELTON y HENRY P. K\RGHNER A TTORNE-Y PatentedMar. 19, 1940 UNITED STATE cosmic mans-ms Raymond G. Bonner, llomie L.Melton, and Henry P. Kirchner, Niagara Falls, N. Y., asaignorl, by memoassignments, to The Oarborundnm Com pany, Niagara Falls, N. Y acorporation of Delaware Application October 27,

' io Clam This invention relates to improved apparatus for themanufacture of granular coated webs of such materials as paper, cloth,or the like and has for an object the provision of improved machin- 5cry for securing a superior product, greater eiiiciency, and/or lowercost of production,

articles. x More specifically, this invention relates to apparatus bythe use of which granular materials can be projected upwardly and-at anoblique angle to an adhesive coated side of a web. 7

It has been found heretofore that superior granular coated websforsuch'uses as abrading can be made by arranging those particles thathave a generally elongated shape in such'a way that these longerparticles project from the web with their longer dimensions normal tothe surface-of the web. Maximum benefit from parti-. cles arranged inthis manner results only when at least a substantial proportion of theparticles in a inasspf abrasive grains are of the elongated type, sincethese particles that are more or less of the same dimension in alldirections can, not

of. coated be oriented with a longer dimension in any' par- '25 tlculardirection. v

r We have found that a faster cutting abrasive coated web can be made byprojecting the particles upwardly and at an oblique angle with respectto the surface of the coated web because these angularly projectedparticles embed themselves in the adhesive coating of the web at'anoblique angle with respect to the surface of the web regardless ofwhether they are of an elongated shape or not. Those particles that areof elongated shape impinge upon the adhesive coating in an endwisemanner and therefore become oriented with their longer dimensionprojecting at an oblique angle from the surface of the web.

Those particles that are. of general irregular 40 shape, of which thereusually is a substantial procoating at an oblique angle insteadof at aright I angle as is the case when apparatus heretofore known has benused. The general result of this upward and at the same time angular,projection of the patricles to the adhesive coated web is a fastercutting abrasive article because substantially all of the particles arearranged on the web like the teeth of a saw and moreover, this result isaccomplished without the necessity of preselecting grains of generallyelongated shape.

An abrasive cloth or paper of this character if used, for example, as asanding belt can bedriven 5 in the direction of inclinationof theparticles so to the adhesive side of the web P; means D for 19:2, SerialNo. siassr as to secure a very rapid cutting or abrading action. Itdriven in the opposite direction, the action is more of a polishing orfinishing action; Thus, a single belt can be employed for both rapidabrading and finishing.

Whi le the degree of inclination can be varied as desired, we have foundthat inclination of the grains at about 15 to to the plane of thebacking gives the best results for rapid cutting.

A- better understanding of our inven ion can be obtained by reference-tothe accompanying drawings in which:

Figure 1 is a diagrammatic elevation of apparatus embodying ourinvention;

Figure .2 isa diagrammatic elevation showing a modification of the graindepositing means;

Figure-3 is-an enlargedview of the electrode assembly shown in Figure,1;

Figure 4 is a view partly insection of a modificfation -oi' -the lowerelectrodes; and

Figured shows a sectional view through the plane V-V ofFlg'ur'e 4. r

The apparatus shown in Figure 1 illustrates our invention in connectionwith apparatus for the manufacture of, abrasive 'coated,webs, andincludes a means A for holding and dispensing a roll 2 of the web P ofpaper, cloth or the like, I means B for applying adhesive to one face ofthe web P; means C for applying granular material 30 causing apreliminary set of the adhesive, and

. means E for drawing the web through the coating apparatus and into thedrying chamber.

The means A ior holding and dispensing the web P comprises, as shown inthe drawings, a 35 'framei that supports the roll 2 of web v1?; an id-'ler roll {forguiding the web; printing rolls 4 and 5 for marking theweb with any desired legend or identification; and an idler roll 1 forguiding the web. I

' The adhesive applying means B comprises, as shown inthedrawings,idlerrolls 8 and 9 for guiding the web; a roll H positioned todip into a pan I! of adhesivena roll, I! for maintaining contact betweenthe web P and the roll II; a drum l5 and an adhesive distributing brushit positioned above the said drum is; and an idler roll H! for guidingthe web as it is brought from the distribupper portion of the feed beltbeing positioned between electrodes 23 and 24 and nearer to theelectrodes 24. The feed belt, with its supporting rollers 42, 42a, 43and 43a, and the electrodes 23 and 24 are all positioned on a carriage50 which is rotatable about the point 40 for cooperation with theadjustable electrodes 23 and 24 in producing different angles ofprojection with respect to the web. If desired, the feed belt 4| canhave a somewhat corrugated surface for preventing relative movement ofthe granular material with respect to the belt.

A better understanding of the construction of a suitable electrode canbe had by reference to Figure 3, which shows in detail one modificationof electrode structure suitable for use in our apparatus. The electrodes23, as shown in Figure 3, are formed of pieces of wood 60 and BI betweenwhich is placed a metal conducting plate 62. We have found itadvantageous to use a distributing plate 62 in order to cause thecharging current to divide and spread substantially evenly over thewooden electrode and also to reduce the unit density of leakage currentupwardly through the wood to its top surface. We prefer to enclose themetal plate rather than have it attached to the bottom of the electrodein order that leakage in other directions than that toward the uppersurface of the electrode may be reduced, A good insulating material,such as glass, can be used instead of wood for the lower piece 60 of theelectrode 23.

As shown in Figure 3, the electrodes are supported on frame members 63which are hung from a support 33 by means of hanger bars 66 of highlyinsulating material such as hard rubber. The upper electrodes 24, whichcan be of any good conducting material, are attached to the bar '27. Thebar is hung from the support 28 by means of the screws 29 and 33 whichare threaded into adjusting nuts 33 and 32, respectively.

The support 28 is slidably mounted on the frame member 33 and isadjustable along a plane parallel to the lower electrode 23. Suchadjustment is provided by means of a handwheel 66 and screw threadedshaft 61, journaled on the frame 33 and engaging a threaded projectingportion 68 of the support 23. The lower electrodes 23 are interconnectedby means of the conductors 26 while the upper electrodes 2 areinterconnected by means of the bus bar 27.

Figures 4 and illustrate a modified form of electrode suitable for useas a lower electrode in our apparatus. As illustrated in the drawings,it comprises a cylinder ii of poorly conducting material, end pieces 72of highly insulating material and a conductor 73 running through the endpieces and through the cylinder.

On the carriage 50 also are mounted rolls 24, 22 and 49, which rolls areadjustable as a unit. for positioning the web between the feed belt 4iand the upper electrodes 2%, and a source 48 I of air of low velocityand relatively large volume A source of eleotromotive force, not shownspecifically in the drawings, but indicated by the positive and thenegative symbols, also is included in the means C for applying granularmaterial to the web P. The source of electromotive force, which iscapable of producing an effective potential difference of about 30,000volts and more, can be one that produces a continuous unidirectionalcurrent, or a pulsating current such as intermittent unidirectionalcurrent, or a current such as is commonly called alternating current.The duration of each pulsation, when pulsating current is produced bythe source of electromotive force, should be such that the particleswill become charged and projected from the feed belt. We have found thatapparatus built in accordance with our invention operates moreeffectively when the lower electrodes are connected to the negativeterminal of the source of the electromotive force and the upperelectrode is connected to the positive terminal. This positive terminalis also grounded as a precautionary measure. The polarity of theelectrodes 23 and 24 can be reversed, however, if it is so desired.

The means C for applying'granular material to the web P comprises also avariable speed driving means 44 and 45 for moving the feed belt 46around'the pulleys 42, 42a, 43 and 53a, and a hopper 47 for catching theexcess grain discharged by the feed belt 4|.

The means D for causing the adhesive to acquire a preliminary setcomprises, as shown in the drawings, an idler roll 49 and a fan blower48 for supplying a large volume of air at a low velocity to the adhesiveand granular coated side of the web P.

The means E for drawing the Web P from the coating apparatus into thedrying chamber comprises, as shown in the drawings, one or more suctiondrums 5i and 52; an idler roll 53; a rack 55 for supporting the web P,and an endless conveyor 54 for transporting loops of the web P to therack The projecting means shown in Figures 1, 2 and 3 of the drawingscomprises a plurality of electrodes interconnected to form an upperelectrode surface and another plurality of electrodes interconected toform a lower electrode surface. We have found it desirable in apparatusfor the purpose disclosed in this application to make both the upper andlower electrode surfaces of a number of smaller units rather than as alarge unit in each case, because it is desired to set up anelectrostatic field that passes through the feed belt and the Web P atan oblique angle. Two large area electrodes when placed close togetherwill set up a field between them that is normal to their surfaces, eventhough one of the electrodes is not positioned squarely above the other,and since there is not sufiicient space between the upper and lowerelectrodes to permit of an appre- 'ciable angular relationship betweenthe web and the field, it is impossible to produce orientation at anyangle appreciably different than 90. By making the upper and lowerelectrodes of separate small units and positioning these small units ineach group at a distance greater than the distance between theinteracting units of the upper and lower electrodes, an electrostaticfield can be set up that will intersect the web P at an oblique angle.The upper and lower electrode surfaces are each made of separate unitsfor the additional reason that it becomes possible thereby to increaseor decrease the breadth of the field by adding or taking away units asthe case may be.

We have found that the upper electrode units aromas can be made of anygood conducting material such as metal, but that the lower electrodeunits serve in a particular manner and preferably aremade of a materialthat will hold back the flow of current that ordinarily would take placewhen a large potential difference is applied to the ordinary electrodesand yet will permit some current to flow to the upper surface of thelower elec' trodes.

The material of which these lower electrodes is made is of considerableimportance in the successful operation of machines built in accordancewith our invention. It appears that a poor conductor of electricity isrequired for these electrodes because some leakage is required in orderto provide sufiicient current to charge the particles that are broughtinto the electrostatic field by the feed belt 4|. substantially preventpassage of the current at the potentials we prefer to use are notsatisfactory because they prevent the projection of the particles fromthe feed belt to theadhesivqcoated web. Metal or other good conductingmaterials permit substantially free and unrestricted passage of thecurrent when the applied electromotive force is sufficient to produceionization of the air between the electrodes, and cause spark-over orarcing. Such arcing or sparkover is detrimental to the manufacture ofsatisfactory abrasive coated webs since each sparkover or are not onlycauses a bare streak ,to occur been given as illustrations of goodconductors.

.lar particles to the degree necessary for their projection by theelectromotive force applied to the electrodes. 1

Other woods than pine and other materials than wood can be used for thelower electrodes. Laminated materials in which one or more of thelaminae are of the type of the material referred to above as goodinsulators are 'not satisfactory, but composite materials, such ascotton fabrics bonded with resinous materials, such as Bakelite orRedmanol, are suitable for the lower electrodes of our apparatus. It ispreferred. however, that when materials of this general character areused, the fibers be so positioned that they lie in such a direction thatwhen the material is formed into an electrode, they will carry thecurrent lengthwise toward the active surface of the electrode.

Our copending application, Serial No. 647,244, filed December 14, 1932,discloses and claims electrodes of poorly conducting material and theiruse in other types of apparatus than that em- Materials that insulateand 24 and thelower electrodes 23.

The metals have the frame I and the web is threaded over the roll I andbetween the printing rolls 4 and 5 and thence in contact with the idlerrolls l,- 8 and 9 to the pressure roll l3 and the adhesive roll II. Theadhesive roll dips into liquid adhesive contained in the adhesive tanki2 and, on the upward movement of travel of the roll I I, a layer ofadhesive isapplied to the web. I

The adhesive coated web P passes between the brush drum i5 and avibrating brush it which evenly distributes the adhesive and smoothsoutany ridges. The web is then guided by the idler rolls l8, l9 andadjustable roll 21 into an elecbetween the electrodes 23 sition of whichis such that it is parallel to the web P in the space between the upperelectrodes The variable speed driving mechanism 44 moves the feed belt4| through the space between the electrodes in the same direction thatthe web P is moved.

In the modification shown in Figure 1, different degrees of angularityof the particles with respect to the web are produced by rotating thecarriage 50 about its axis to such a position that the web makes thesame angle with the vertical as the angle at which it is desired to havethe particles take with respect to the web. The upper group ofelectrodes is then shifted parallel to the web until they are sopositioned that a substantially vertical field will be establishedbetween the upper and lower electrodes when the electromotive force'isapplied. Different degrees of angularity are secured wit themodification shown in Figure 2 by the simple expedient of shifting theupper group of electrodes horizontally to the right or left, as the casemay be, and adjusting the guide roll 49 up or down, as required toposition the web at the same angle with the vertical as it is desired tohave the particles take with respect to the web.

The granular material, as it moves intoand through the field, becomeselectrically charged and leaves the beltto move upwardly toward theadhesive coated web as aspray or rain of particles spacedv apart fromone another. The upwardly moving particles strike the adhesive coatedweb and become attached thereto.

The forces produced by the electric field turn those particles that areof elongated shape so that their major axes are parallel to the lines offorce of the field. These oriented, elongated par- 1 Observation of thespace between the upper and lower electrodes, when the machine is inoperation, shows a distinct bluish color and freedom from localizedarcing or spark-over. The bluish coloration indicates that a coronafield exists between the upper and lower electrodes. The grain particleson the belt may receive their negative electrostatic charges byconduction through the fibers of the belt, byinduction, or by the coronadischarge from the bottom .electrode through the belt, and possibly by acombination of these. Whatever is the mechanism of the transmission ofelectrostatic charges to the grains, the fact remains that the granularparticles receive suflicient electrostaticv charge to cause them to beforcibly driven upwardly through the'strong electrostatic field from thefeed belt against the under side of the adhesive coated web. As pointedout above, the elongated particles not only are projected upwardly butare oriented and projected.

In operating our apparatus, we prefer to space the electrodes 23 and 24about one inch apart and to apply a potential difierence of between30.000 and 100 ""3 volts. The potential difi'erence applied to theelectrodes is adjusted to such value that the abrasive particles on thefeed belt 4| become charged and are propelled toward the upper plate 24and strike the adhesive coating on the web P with suflicient force topartially embed themselves and adhere thereto. We have found, otherfactors remaining constant, that the electromotive force required toelectrostatically propel the charged granules into engagement with theadhesively coated web varies in proportion to the size or mass of thegranules; that is, a higher electromotive force is required for largegrainthan for a smaller size. For grits of from 50 to 200 mesh andfiner, we have found that potential differences of from 30,000 to 50,000volts are suitable. Coarser grits require higher voltagcs and in thecase of grits as large as 16 mesh, an electromotive force of about90,000 volts may be required to orient and propel the granular materialfrom the feed belt to the adhesive coated web. Thus, by means of thevariable voltage apparatus, the potential difierence applied to theelectrodes can be adjusted to such a value that grain of a certainspecific size will be electrically deposited on the adhesive coating,whereas any grain of a larger size, which might be present on the feedbelt, will remain and be carried into the bin 41.

We have found that inasmuch as the grain is raised from the feed belt byelectrostatic forces and that the quantity of grain that is raised iscontrollable by adjustment of the potential difference supplied to theelectrodes, an excess of grain on the feed belt is desirable for theproduction of a uniform coating on the web. If it is found that thedensity of the coating being applied to the web is lighter than desired,an increase in the potential difference applied to the electrodes willcause more grain to rise and become embedded in the adhesive coating ofthe web. Conversely, if a heavier coating than is desired is beingdeposited on the adhesive coated web, a decrease in the potentialdifference applied will operate to make the coating less dense. Afterbeing coated with granular material, the web is then moved through azone in which the adhesive is given a preliminary set in order to fixthe particles in the positions they took when they were deposited uponthe adhesive coated web. The position of the granular coated web whileit is moving through'this zone is such that the justment to meetdifferent conditions.

grains hang substantially vertically like tiny pendulums. Those grainsthat have been oriented in the desired positions remain so orientedbecause of gravitational attraction, and those grains that impinged uponthe adhesive coating at any other angle than the desired angle'arepulled into the desired positions by the action of gravity. Thus,gravity is utilized not only to preserve a particular orientation but toproduce the desired orientation.

Apparatus constructed in accordance with our invention has the advantagethat it is simple to construct, easy to operate, and flexible as to ad-There are no complicated mechanical movements nor delicate parts to getout of order. when once adjusted to produce the desired type of coatingit operates with no more attention than is required in the ordinary typeof coating machine and when adjustments are necessary, they can be madevery simply by changing the applied potential difference or by changesin the relative positions of the various parts of the apparatus.

Raising or lowering of the frame 50, which carries with it the graindepositing apparatus, and a slight shift in the relative positions ofthe upper and lower electrodes, is all that is necessary to produce websin which the grains are positioned at different angles. When the frame50 is more nearly horizontal than vertical, the electrodes 23 and 24being positioned to produce a substantially vertical field, theparticles are deposited upon the adhesive coated web at an angle verymuch smaller than the angle at which they are deposited when the frameis in a position less nearly horizontal. The ease with which this changefrom a small angle to a relatively large angle, or vice versa, can bemade is of great advantage.

The control of the density of the coating on the web by the change infield intensity or by the use of a different number of lower electrodes,either large or small, also is of considerable advantage because itpermits close adherence to standards of quality as to weight of grainper unit of surface and also because it makes it possible to eliminatecoarse grits that might get into the grain mixture.

Another simple adjustment that can be made with apparatus made inaccordance with our invention is the alteration of the density of thegranular coating by moving the web closer to the feed belt. The grainsare projected upwardly as a rain or spray, not as a body, and not all ofthe particles raised by the electrostatic forces are projected the samedistance. By moving the web closer to the feed belt, those particleswhich would otherwise fallback to the feed belt are caught by theadhesive coating and held.

Apparatus constructed in accordance with our invention has the advantagethat gravitational attraction serves to assist in the orientation of theparticles on the web and to preserve the desired orientation once it hasbeen secured. The position of the web while the adhesive is yieldable issuch that the particles tend to turn into vertical positions if they arenot already arranged in that direction, and since the web is at thepreferred angle with respect to the vertical the particles thereforeassume the preferred angularity. This advantageous use of gravitationalforce has not been found in any of the machines heretofore known forapplying granular materials to webs.

Other advantages will be apparent from the foregoing disclosure to thoseskilled in the art and while specific embodiments have been used toillustrate our invention, it is to be understood that the invention isnot limited to those embodiments but is defined by the appended claims.

We claim:

1. Apparatus for the manufacture of granular coated webs comprisingmeans for supporting an adhesive coated 'web with an adhesive sidedownward, a plurality of interconnected electrodes spaced apart fromeach other and positioned, above said web, a plurality ofinterconnected, electrodes spaced apart from each other and positionedbelow said web, the interacting electrodes on either side of thewebbeing QJMBS so positioned that a line drawn through the longitudinalaxes of any pair of interacting electrodes will intersect the plane ofthe web at an oblique angle, and means located above said lowerelectrodes and below said webifor supporting granular material.

2. Apparatus for the manufacture of granular coated webs comprisingmeans for movably sup- 7 porting an adhesive coated web with an adhesive10 side downward, a plurality of interconnected electrodes spaced apartfrom each other and posi- .tioned above said web, a plurality ofinterconnected electrodes spaced apart from each other and positionedbelow said web, the interacting electrodes on either side ofthe webbeing so positioned that a line drawn through the longitudinal axes ofany pair of interacting electrodes will intersect the planaof the web atan oblique angle,

and movable means located above said lower so electrodes and below saidweb for supporting granular material. I I

3. Apparatus for the manufacture of granular coated webs comprisingmeans for supporting an adhesive coated web with the adhesive-side down-26' ward, a plurality of interconnected electrodes spaced apart fromeach other and positioned above said web, a plurality'of interconnectedelectrodes spaced apart from each other and positioned below said web,the interacting elecgo trodes on either side of the web being sopositioned that a line drawn through the longitudinal axes of any pairof interacting electrodes will intersect the plane of the web at anoblique angle, means located above said lower electrodes and 35 belowsaidweb for supporting granular material, and means for applying apotential difierence to the upper and lower electrodes, said apparatusbeing adapted to electrostatically project granular material against thedownwardly facing adhesive surface of said web.

4. Apparatus for the manufacture of granular coated webs comprisingmeans for movably supporting an adhesive coated web with the adhesiveside downward, a plurality of interconnected elecll trodes spaced apartfrom each other and positioned above said web, a plurality ofinterconnected electrodes spaced apart from each other and positionedbelow said web, "the interacting electrodes on either side of the webbeing so 66 positioned that a line drawn through the longitudinal axesof any pair of interacting electrodes will intersect the plane of theweb at an oblique angle, movable means located above' said lowerelectrodes and below said web for supporting as granular material, andmeans for applying a potential diilerence to the upper and lowerelectrodes, said apparatus being adapted to electrostatically projectgranular material against the downwardly facing adhesive surface of saidweb. 5. Apparatus for the manufacture of granular coated webs comprisingmeans for movably supporting an adhesive coated web with an adhesivecoated side downward, a plurality of intercom nected electrodes of goodconducting material 65 spaced apart from each other and positioned abovesaid web, a plurality of interconnected electrodes of poorly conductingmaterial spaced apart from each other and positioned below said web, theinteracting electrodes on either side of '70 the web being so positionedthat a line drawn through the longitudinal axes of any pair ofinteracting electrodes will intersect the plane of the web at an obliqueangle, movable means located above said lower electrodes and below saidu web for supporting granular material, and means for applying apotential diflerence to-said upper and said lower electrodes. saidapparatus being adapted to electrostatically project granular materialagainst the downwardly facing adhesive surface of the web. 6. Anapparatus for the manufacture of granular coated webs comprising aplurality of electrodes of good conducting material spaced apart fromeach other and positioned above a plurality of electrodesof amaterialhaving suflicient conductivity to permit a leakage curent toflow therethrough, but of sufllcient resistance to prevent spark-over orarcing to the upper electrodes, means for applying a potentialdifference to the said upper and lower electrodes, means for supportingan adhesive coated web between said electrodes and with an adhesivecoated surface downward, the interacting electrodes on either side ofthe web being so positioned that a line drawn through the longitudinalaxes of any pair of interacting electrodes will intersect the plane ofthe web at an oblique angle, movable means v located above said lowerelectrodes and below said web for supporting granular material, andmeans for applying a potential difference to said upper and said lowerelectrodes, said apparatus being adapted to electrostatically projectgranular material against the downwardly facing adhesive surface of theweb. A

7. Apparatus for the manufacture of granular coated webs comprisingelectrostatic means for projecting the granular material verticallyupward, means for movably supporting an adhesive coated web at anoblique angle with respect to .the vertical and with an adhesive coatedside downward to receive the upwardly projected granular material, andmeans for causing the adhesive to acquire a preliminary set locatedadjacent to said electrostatic projecting means and in a positionsubsequent thereto with respect to the directionof movement of said web.

8. Apparatus for the manufacture of granular coated webs comprising theelectrostatic means for projecting granular material upwardly at anoblique angle with respect to the vertical, means for movably supportingan adhesive coated web in a horizontal position with an adhesive coatedsurface facing downward to receive the upwardly projected granularmaterial, and means for causing the adhesive to acquire a preliminaryset without disturbing the positions of the deposited granules, saidmeans being located adjacent to said electrostatic projecting means andin a an adhesive coated surface downward, said electrostatic projectingmeans and said web supporting means being positioned with respect toeach other to cause the projected granular material to be deposited onthe web at an oblique angle with respect to the surface of said web,means for supplying granular particles between said web and the saidlower electrodes and means for causing the adhesive to acquire apreliminary set located adjacent to said electrostatic means forprojectoblique angle, comprising electrostatic means for projecting thegranular material upward, means for movably supporting an adhesivecoated web at an oblique angle with respect to the upward projection ofsaid granules and with an adhesive side downward to receive the upwardlyprojected granular material.

RAYMOND C. BENNER. ROMIE L. MELTON. HENRY P. KIRCHNER.

